In 1999, EgyptAir flight 990 ditched into the sea 30 minutes after it took off from New York, killing all 217 people on board. A subsequent investigation by the American National Transportation Safety Board (NTSB) concluded that the cause of the crash had been a deliberate act by the relief first officer, but an Egyptian inquest into the incident found that the crash had been caused by mechanical failure.
On Thursday, French investigators confirmed that the Germanwings plane which crashed into the French Alps on Tuesday, killing all 150 people on board, was brought down intentionally by the co-pilot. So are there parallels to be drawn between the EgyptAir flight and the Germanwings crash?
Andreas Lubitz, the 28-year-old co-pilot blamed for Tuesday's crash, is believed to have locked himself into the cockpit when his captain left the cockpit, possibly to use the toilet.
"At that moment, the co-pilot is controlling the plane by himself," a French prosecutor said. "While he is alone, the co-pilot presses the buttons of the flight monitoring system to put into action the descent of the aeroplane. This action on the altitude controls can only be deliberate."
Similarly, in 1999, one of the two pilots of EgyptAir flight 990, Gamil el Batouty, assumed sole control of his plane shortly before directing the 767 into a 40 degree dive, the NTSB said after it finished its investigation into the incident. Most passengers will never experience a descent of more than five degrees.
According to the NTSB's analysis of the plane's voice recorder, when the other pilot Captain el Habashy returned to the cockpit, he desperately tried to reverse the jet's descent, but el Batouty thwarted his colleague's efforts to save the plane by shutting down its engines, The Atlantic reports.
The NTSB later leaked its conclusion that el Batouty most likely committed suicide, taking all 217 passengers on board with him. On a garbled tape recovered from the crash, el Batouty seemed to declare, "I place my fate in the hands of God" several times before shutting off the plane's engines.
Investigators from the Egyptian Civil Aviation Authority disagreed with the NTSB's findings, concluding instead that the crash had been caused by mechanical failure.
Accepting that a pilot may have been to blame for a crash is complicated for any airline, not least of all due to the financial implications such admissions carry. Experts say that family members of the victims of the Germanwings plane crash could be in line for up to £100 million in compensation, the Daily Mail reports.
Also, identifying psychological disturbance in pilots is difficult, experts say.
The International Civil Aviation Organisation (ICAO), recommends that someone with depression should not fly a plane, Reuters says. But the Manual of Civil Aviation Medicine also says that testing crews for psychological disorders is "rarely of value" and not "reliable" in predicting mental problems.
Germanwings's parent company Lufthansa immediately introduced a new "two person rule" ensuring that no pilot is left alone in the cockpit after Tuesday’s tragedy. EasyJet and Air Berlin also adopted the rule, which is already standard for American airlines. But aviation experts say the new policy is likely to be just the beginning of longer story for the budget carrier.